Piezoelectric properties in perovskite 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free ceramics

TLDR

Lead‑free piezoelectric ceramics with composition 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 were prepared by conventional solid‑state sintering and their piezoelectric and electromechanical properties were measured across temperature. The KNN‑based ceramic exhibits a Curie temperature of 368 °C, an orthorhombic‑tetragonal transition near 35 °C, room‑temperature dielectric permittivity of 1380, loss of 2 %, piezoelectric coefficients k33≈62 % (d33≈265 pC/N) and k31≈30 % (d31≈−116 pC/N), and shows temperature‑dependent maxima and elastic softening akin to PZT while displaying both soft and hard piezoelectric behavior due to distinct orthorhombic and tetragonal domain states.

Abstract

Lead-free piezoelectric ceramics, with the nominal composition of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 (KNN-LS5.2), were synthesized by conventional solid-state sintering, and the piezoelectric and electromechanical properties were characterized as a function of temperature. The Curie temperature of the KNN based perovskite material was found to be 368°C with an orthorhombic-tetragonal polymorphic phase transition (TO-T) temperature at approximately ∼35°C. The room temperature dielectric permittivity (ε33T∕ε0) and loss were found to be 1380 and 2%, respectively, with piezoelectric properties of k33∼62% and d33∼265pC∕N and k31∼30% and d31∼−116pC∕N. The temperature dependence of the properties mimicked the compositional variation seen in the proximity of a morphotropic phase boundary [e.g., lead zirconate titanate (PZT)], with a maxima in the dielectric and piezoelectric properties and a corresponding “softening” of the elastic properties. Unlike that found for PZT-type materials, the modified KNN material exhibited characteristics of both “soft” and “hard” piezoelectricities owing to the distinctly different domain states associated with orthorhombic and tetragonal phases.